Bank of America strategist Michael Hartnett warns the AI stock bubble is ready to burst, citing warning signs that mirror the dot-com crash of 2000.

What happened: Hartnett, managing director and chief investment strategist at Bank of America's research arm, issued guidance to clients warning that the current AI frenzy will end in a bubble burst. His research identified red flags including only 21 stocks driving the S&P 500 to a record high—just one more than the 20 stocks that led the index at the peak of the dot-com bubble before it crashed in 2000.

Why it matters: The concentration of market gains in a tiny number of stocks, combined with what Hartnett called 'speculative' and 'exponential price action,' overvaluation of unprofitable firms, extreme imbalance with just 10 stocks comprising two-fifths of the index's power, and upwards of 330 S&P components sitting 20–40% below their previous highs, suggests the market may be vulnerable to a significant correction. These patterns echo past financial crises.

What to watch: To mitigate potential damage, Hartnett and his team recommend leaning into bonds—a historically reliable but lower-profile area of the market—as a defensive strategy against a possible market downturn.